In a wireless communications system such as a cellular mobile communications system, a wireless local area network (WLAN for short), or a fixed wireless access (WLAN for short) system, a communications node such as a base station (BS for short), an access point (AP for short), a relay station (RS for short), or user equipment (UE for short) generally has capabilities of transmitting a signal of the communications node and receiving a signal of another communications node. Because a radio signal is greatly attenuated on a radio channel, compared with a signal transmitted by a transmit end of a communications node, a radio signal from another communications node is already quite weak when arriving at a receive end of the communications node. For example, a power difference between a received signal and a transmitted signal of a communications node in a cellular mobile communications system typically reaches 80 dB˜140 dB. Therefore, to avoid interference from a transmitted signal of a communications node to a received signal of the same communications node, different frequency bands or time periods are usually used to distinguish between radio signal sending and reception. In a wireless communications system that uses time division duplex (TDD for short), a same carrier is used as a carrier for a sent signal and a received signal, and signal sending and reception are performed in different timeslots on the carrier to ensure complete separation between reception and sending, thereby avoiding interference from sending to reception. In frequency division duplex (FDD for short), different carriers spaced apart by a specific quantity of guard carriers are used for sending and reception. A normal practice is: sending and reception are performed respectively on two spectrum-paired carriers, and there is a guard band (where the guard band is usually 190 MHz) between the two carriers, to prevent mutual interference between a receiving device and a neighboring sending device.
In the prior art, a radio frame in a TDD system is divided into multiple timeslots in terms of time, and each timeslot is configured for a downlink or configured for an uplink, so that the system can configure a proper uplink-downlink timeslot ratio according to an uplink-downlink service volume ratio. For example, in a TDD cellular mobile communications system, an uplink-downlink service volume ratio is usually 1:3. Therefore, uplink and downlink timeslots are typically configured at a ratio of 1:3. However, because each timeslot in the TDD system is only used to receive or send a signal in a fixed time period, spectrum utilization is still not high. In an FDD mode, because spectrum-paired carriers are usually used in FDD, when a symmetric service (that is, amounts of sent data and received data are equivalent) is supported, uplink and downlink spectrums can be fully used; however, for an asymmetric service (that is, amounts of sent data and received data are greatly different), carrier spectrum utilization is greatly reduced. In conclusion, the prior art has a problem of low carrier spectrum utilization.